Objectives: 1. To isolate and extensively purify large quantities of enzymes which possess certain predetermined characteristics and are capable of degrading the following amino acids: glutamine, arginine, citrulline, histidine, and serine. 2. To study the effects of prolonged enzyme treatment on plasma amino acids in mice and larger animals. 3. Employing our new enzyme preparations to evaluate the antitumor efficacy of single- and multi-enzyme therapy, as well s enzyme therapy combined with immuno- and, or chemo-therapy. 4. To determine the toxicity of new enzymes in mice and larger animals. 5. If needed, to chemically or physically alter the enzymes so as to extend their biological half-life and lower their immunogenicity.